Inserter for expanding an expandable interbody fusion device

ABSTRACT

An elongate inserter has a distal end releasably connected to an expandable interbody fusion device and a proximal end including a trigger actuator. The interbody fusion device comprises a superior endplate and an inferior endplate that are movable in an expansion direction relative to each other in the intradiscal space. The inserter includes a lifting platform and an elevator that define cooperatively engaging ramps and ramps surfaces that upon operation of the trigger actuator cause the superior and inferior endplates to move relatively away from each other. A driver is supported by the inserter for pushing an insert into the expanded device between the superior and inferior endplates.

FIELD OF THE INVENTION

The subject invention relates generally to the field of spinal implantsand more particularly to an inserter for expanding an expandableinterbody fusion device and inserting an insert therewithin.

BACKGROUND OF THE INVENTION

Spinal implants such as interbody fusion devices are used to treatdegenerative disc disease and other damages or defects in the spinaldisc between adjacent vertebrae. The disc may be herniated or sufferingfrom a variety of degenerative conditions, such that the anatomicalfunction of the spinal disc is disrupted. Most prevalent surgicaltreatment for these conditions is to fuse the two vertebrae surroundingthe affected disc. In most cases, the entire disc will be removed,except for a portion of the annulus, by way of a discectomy procedure. Aspinal fusion device is then introduced into the intradiscal space andsuitable bone graft or bone substitute material is placed substantiallyin and/or adjacent the device in order to promote fusion between twoadjacent vertebrae.

Certain spinal devices for achieving fusion are also expandable so as tocorrect disc height between the adjacent vertebrae. Examples ofexpandable interbody fusion devices are described in U.S. Pat. No.6,595,998 entitled “Tissue Distraction Device”, which issued on Jul. 22,2003 (the '998 patent), U.S. Pat. No. 7,931,688 entitled “ExpandableInterbody Fusion Device”, which issued on Apr. 26, 2011 (the '688patent), and U.S. Pat. No. 7,967,867 entitled “Expandable InterbodyFusion Device”, which issued on Jun. 28, 2011 (the '867 patent). The'998 patent, the '688 patent and the '867 patent each disclosessequentially introducing in situ a series of elongate inserts referredto as wafers in a percutaneous approach to incrementally distractopposing vertebral bodies to stabilize the spine and correct spinalheight, the wafers including features that allow adjacent wafers tointerlock in multiple degrees of freedom. The '998 patent, the '688patent and the '867 patent are assigned to the same assignee as thepresent invention, the disclosures of these patents being incorporatedherein by reference in their entirety.

One issue that has arisen regarding such interbody fusion devices thatuse inserts or wafers to incrementally expand such devices is thedetermination of when full expansion has been achieved as a result ofligamentotaxis and no further inserts may be inserted. It is thereforedesirable for a surgeon to know when a sufficient number of inserts hasbeen introduced to stabilize the spine and correct spinal height andwhether any additional inserts may be introduced.

Accordingly, there is a need for a method and instrument to expand anexpandable interbody fusion device and introduce inserts therein and todetermine when proper expansion of the device has been achieved and nofurther inserts may be introduced.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an inserter for expanding anexpandable spinal implant, such as an interbody fusion device and tointroduce inserts therein after the implant has been expanded. It is afurther object of the invention to also provide a method whereby fullexpansion of the expandable device may be determined in a manner suchthat a user may ascertain that no additional inserts may be inserted.

DESCRIPTION OF THE FIGURES

FIG. 1 is a top perspective of an inserter in accordance with oneembodiment of the present invention releasably attached to andexpandable interbody fusion device, shown unexpanded.

FIG. 2 is an exploded perspective view of the distal end of the inserterof FIG. 1.

FIG. 3 is an enlarged view of the exploded portion of FIG. 2.

FIG. 4 is a longitudinal cross-sectional view of the inserter of FIG. 1.

FIG. 5 is a top perspective view of an insert used in an expandablespinal interbody fusion device of the subject invention.

FIG. 6 is a bottom perspective view of the insert of FIG. 5.

FIG. 7 is a partial perspective cross sectional view of the inserter ofFIG. 1 releasably attached to an expandable interbody fusion device witha first insert of FIG. 5 having been inserted therein.

FIG. 8 a is a partial side perspective view of the inserter andexpandable interbody fusion device bottom of FIG. 7 showing a secondinsert entering the interbody fusion device at the proximal end andbelow the first insert.

FIG. 8 b is an enlarged view of a portion of FIG. 8 a showing therelative positions of the first and second inserts.

FIG. 9 is a partial side perspective view of the inserter and expandableinterbody fusion device of FIG. 8 a showing the second insert fullyinserted into the interbody fusion device.

FIG. 10 is a proximal perspective view of an expanded spinal interbodyfusion device with a guide pin releasably connected thereto subsequentto the inserter having been the detached from the guide pin with insertsnot being shown for clarity.

DESCRIPTION OF THE EMBODIMENTS

For the purposes of promoting and understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

Turning now to FIGS. 1-3, inserter 10 is shown for use in expanding insitu a spinal implant, such as an interbody fusion device 100, and forinserting inserts into the expanded device 100. The expandable interbodyfusion device 100 includes a first element, such as superior endplate112 and a second element, such as inferior endplate 114, as shown inFIGS. 2-3. The height across the superior and inferior endplates 112,114 in the unexpanded condition as illustrated in FIG. 1 is less thanthe normal anatomic height of a typical intradiscal space. The inventioncontemplates expanding the interbody fusion device 100 by the inserter10 to ultimately restore the normal anatomic height of the disc spaceand thereafter inserting a series of inserts, such as interlockinginserts 200, as will be described, to form a stack of inserts 200between the expanded superior and inferior endplates.

The superior endplate 112 is elongate and comprises a hub 116 that issized and configured to fit within a cavity 118 of the inferior endplate114 for telescoping movement therewithin upon expansion. The lowersurface 120 of the hub 116 includes a shaped configuration defined byinsert mating features 122 (see FIG. 7) that are substantially identicalto the mating features on the lower surface of each insert 200, as willbe described. The superior endplate 112 includes a graft chamber definedby an opening 124 extending therethrough and inferior endplate 114includes a graft chamber defined by an opening 126 extendingtherethrough for receipt of a suitable bone filler or bone graft topromote fusion between opposing vertebral bodies of a spine. Furtherdetails of interbody fusion device 100 are described in commonlyassigned U.S. patent application Ser. No. 13/795,054 entitled“Expandable Interbody Fusion Device with Graft Chambers”, filed on Mar.12, 2013 (“the '054 Application”) and incorporated herein by reference.

Details of the interlocking insert 200 are shown in FIGS. 5-6. Theinsert 100 is elongate and has an upper surface 202 and a lower surface204, both of which are generally planar so that the inserts can form astable stack within the interbody fusion device 10 upon expansion.Insert 200 includes a trailing rear end 206 and a leading front end 208.The rear end 206 is formed substantially in the form of a horseshoe,with a pair of spaced opposing arms 212 and 214 defining an openrearward facing generally U-shaped opening 216. The surface 218 betweenthe upper surface 202 and the lower surface 204 at the base of opening216 defines a pushing surface 218 for receipt of a driver of inserter10, as will be described. The opening 216 at the rear end of each insert200 is provided to allow bone graft material to flow into the device 100through the insert openings 216 and into the openings 124 and 126extending through the superior endplate 112 and the inferior endplate114, respectively. The rear end 206 includes a flat surface 212 a and214 a, respectively at the free end of each arm 212 and 214 and a flatsurface 208 a on the leading front end 208 of the insert 200.

The insert 200 includes several features for interlocking engagement tothe hub 116 and to adjacent inserts 100 in a complementary interlockingmating interface. One particular feature includes a series of lockingelements defined by resiliently deflectable prongs 220 that projectoutwardly above the upper surface 202 of the insert 200 in the directionof expansion of device 100. A complementary series of locking surfaces222 are defined in the lower surface 204 of the insert 200 for resilientengagement with the prongs 220 as wafers are inserted into device 100 toform a stack. The lower surface 204 of each insert 200 as shown in FIGS.5 and 6 also defines a T-slot configuration 224 for mating with a T-barconfiguration 226 on the upper surface 202 of a successive insert 100.In the illustrated arrangement, there are two prongs 220 extendinggenerally linearly and substantially centrally along the elongatelongitudinal direction adjacent the front end 208 of insert 200. Thestructure and function of insert 200 and the prongs 220 and lockingsurfaces 222 are more fully described in the '054 Application. However,unlike wafers 100 described in the '054 Application, the inserts 200described herein do not function to assist in the separation of superiorendplate 112 and inferior endplate 114 or any subsequent inserts 200inserted into interbody fusion device 100 as that lifting and functionis provided by inserter 10.

Turning again now to FIGS. 1-3, details of the inserter 10 aredescribed. Inserter 10 comprises an elongate barrel 12 having a distalend 12 a and a proximal end 12 b. A trigger actuator 14 to effectexpansion of device 100 and insertion of inserts 200 into device 100after expansion is provided at the proximal end 12 b of barrel 12. Acartridge 15 supported by barrel 12 on the underside thereof contains aplurality of inserts 200 to provide a supply of inserts 204 insertinginto device 100 by inserter 10.

The distal end 12 a is shown in exploded detail in FIGS. 2-3. The barrel12 includes a lower track 16 and an upper track cover 18. An elongateguide pin 20 is supported by barrel 12, the distal end 20 a of the guidepin 20 being threaded for releasable threaded engagement into a suitablethreaded opening in the proximal end of the inferior endplate 114. Theproximal end 20 b of guide pin 20 is provided with a threaded knob 22for compressing the barrel 12 and thereby the inserter to the device100. The track cover 18, in one arrangement, includes a pair of opposingtabs 18 a that engage corresponding notches 128 at the proximal end ofthe inferior endplate 114 to assist in rigidly securing the barrel 12 tothe device 100. It should be appreciated that other securement structuremay be used to releasably attach the barrel 12 and thereby inserter 10to the device 100.

The distal end 12 a of barrel 12 supports a lifting platform 24 and anelevator 26. The lifting platform 24 is coupled at its proximal end 24 aby a boss 24 b or other suitable projection to a lifting platform link28. The boss 24 b is suitably received and retained in opening 28 a atthe distal end of link 28. The lifting platform 24 is axiallytranslatable relative to elevator 26 upon axial translational movementof link 28 which is coupled to an actuator, such as trigger actuator 14at its proximal end, as will be described. Link 28 is supported by track16 for translational movement within a track channel 16 a extendingaxially along track 16. Inserts 200 or movably supported in a lineararray on link 28 within the channel 16 a. It should be appreciated thatactuators other than trigger actuators may be used with the inserter 10described herein.

Elevator 26 comprises a proximal end 26 a and a distal projecting end 26b. The proximal end 26 a is suitably affixed to the track 16 and, in theparticular arrangement being described, remains in a fixed positionrelative to lifting platform 24 and inferior endplate 114 as liftingplatform is translationally moved. The proximal end 26 a defines achannel 26 c for receipt of the proximal end 24 a of lifting platform24. The lifting platform 24 and elevator 26 may in one arrangement be adisposable component and replaced by a new unused lifting platform 24and elevator 26 for subsequent procedures.

The distal projecting end 26 b of elevator 26 includes a lowersubstantially flat surface 26 c and an upper surface 26 d, generallyparallel to lower surface 26 c. Projecting end 26 b is configured toextend within inferior endplate 114 with lower surface 26 c supported byan interior surface 114 a (see FIG. 7). Upper surface 26 d is formed tohave a series of axially extending ramp surfaces 26 e extendingtherewithin, three such ramp surfaces 26 e being illustrated. Liftingplatform 24 includes at its distal end 24 b an upper substantially flatsurface 24 c and a lower surface 24 d, generally parallel to uppersurface 24 c. Upper surface 24 c is configured to engage and supportsurface 205 at the underside of insert 200 (see FIG. 6) as well as thelower surface 120 of superior endplate 112 which has mating features 122that are substantially identical to the mating features on the lowersurface of each insert 200. Lower surface 24 d is formed to have aseries of axially extending ramps 24 e, three of which are shown. Ramps24 e projecting downwardly from lifting platform 24 and ramp surfaces 26e extending within elevator 26 are configured to have suitably inclinedsurfaces such that upon axial translational movement of lifting platform24 relative to elevator 26 ramps 24 e engage ramp surfaces 26 e to causelifting platform 24 to move upwardly and separate from elevator 26.

Lifting platform link 28 includes thereon an upper surface 28 a on whichthe inserts 200 are movably supported in a linear array. Link 28includes a spring element 28 b having an inclined surface for engagingan insert 200 and moving such insert upwardly into an insertion positionfrom track 16 during axial transit along link 28. A pair of cantileveredspring projections 28 d and 28 e may be spaced axially along link 20 ina manner to substantially prevent retrograde movement of inserts 200along link 28.

Barrel 12 further supports a driver 30 for axial translational movementwithin the barrel 12. The proximal end of driver 30 is coupled totrigger actuator 14 to effect translational movement of the driver, aswill be described. The distal end of driver 30 comprises a pushingsurface 30 a sized and configured to enter into the opening 216 of aninsert 200 to engage pushing surface 218 and push the insert 200 intothe device 100 upon axial distal movement of driver 30.

Turning now to FIG. 4, the details of the trigger actuator 14 of theinserter 10 and its function are described. Trigger actuator 14comprises a bar linkage mechanism 31 comprising a first bar 32 and asecond bar 34. The lower end of each bar 32 and 34 is pivotallyconnected to a handle 36 by a pivot pin 38. Pin 38 slides within a camtrack 40 supported on handle 36. The upper end of bar 32 is pivotallyconnected to the proximal end of driver 38 pivot pin 42. The upper endof bar 34 is pivotally connected to the proximal end 12 b of barrel 12by a pivot pin 44. Handle 36 is pivotally connected to barrel 12 by apivot pin 46. A curved cam member 48 is attached at its lower end 48 ato handle 36 with upper end 48 b extending though barrel 12. Cam member48 upon squeezing movement of the handle 36 toward barrel 12 engages acam following surface 50 on barrel 12 to initially pull lifting platformlink proximally. The bar linkage mechanism 31 of the trigger actuator 14is structured to move lifting platform link 28 and driver 30independently of each other and with suitable time delays between suchmovements based on the configuration of the cam track 40. The driver 30is returned to its original starting position when the handle 36 isreleased. Thus, during a single stroke operation of trigger actuator 14the lifting platform 24 is lifted relative to elevator 26, driver 30pushes an insert 200 into the device 100, lifting platform 24 isretracted relatively toward elevator 26 and finally driver 30 isretracted from device 100. Such single stroke of operation is initiatedwhen handle 36 is in the starting position of FIG. 4 and is completedwhen handled 36 is released and returns to its starting position.

Turning now to FIGS. 7-9 the use of inserter 10 to expand the device 100and insert one or more inserts 200 to form an interlock stack is furtherdescribed. FIG. 7 illustrates a condition of the expansion of device 100wherein a first insert 200 has been positioned between superior endplate112 and inferior endplate 114 with prongs 220 suitably interlockinglyengaging the mating features 122 at the lower surface of hub 116. Itshould be understood that to insert the first insert 200 the inserter 10and the method described herein were similarly employed. A subsequentinsert 200 a is shown on spring element 28 b with the insert 200 ahaving been lifted by spring element 28 b into an insertion positionfrom channel 16 a of track 16 during axial advancement distally bydriver 30. In this condition the ramps 24 e of lifting platform 24 arenot deployed relative to ramp surfaces 26 e of elevator 26. Uppersurface 24 c of lifting platform 24 is in contact with and supports theunderside surface 205 of insert 200.

Upon operation of trigger actuator 14, lifting platform link 28 istranslated proximally causing ramps 24 e to engage and ride upwardlyalong ramp surfaces 26 e of elevator 26 thereby causing during suchtranslational movement the lifting platform 24 to move upwardly and awayfrom elevator 26. Such movement lifts insert 200 together withinterlocked superior endplate 112 in the direction of expansion anincremental distance slightly greater than the thickness of insert 200a. With the bar linkage mechanism 31 of trigger actuator 14 configuredto temporarily hold this position for a certain period of time,continued operation of trigger actuator 14 moves pusher 30 distallyuntil the pushing surface 30 a of driver 30 causes the front end 208 aof subsequent insert 200 a to enter device 100 between lower surface 204of a previously inserted insert 200 and inferior ledge 114 b of theinferior endplate 114, as shown in FIGS. 8 a and 8 b. At a point whenfront end 208 a has entered a certain distance, D, continued operationof trigger actuator 14 causes lifting platform link 28 to translatedistally causing ramps 24 e to slide downwardly along ramp surfaces 26 ethereby retracting lifting platform 24 toward elevator 26. Furtheroperation of trigger actuator 14 causes driver 30 to move axiallydistally pushing insert 200 a fully into device 100 with little furtherresistance until the prongs 220 engage locking surfaces 222. Asillustrated in FIG. 9, once insert 200 a is completely inserted prongs220 suitably interlock with locking surfaces 222 of previously insertedinsert 200. When handle 36 is released the driver 30 is drawn proximallya sufficient distance within barrel 12 to be positioned to receiveanother insert 200 b supported within track channel 16 a, if necessary.For illustrative purposes, wherein inserts 200 and 200 a each have alength of approximately 25 mm in the thickness of approximately 1 mm,distance D may be a minimum of approximately 2-3 mm.

It should be appreciated that upon when operation of trigger actuator 14lifting platform 24 is incapable of physically reaching the desiredelevation (which is approximately slightly greater than the thickness ofan insert 200 and determined by the bar linkage mechanism 31), furtheroperation of the trigger actuator 14 during any given stroke will besubstantially prevented. Such resistance will provide tactile feedbackto the surgeon who will recognize that the device 100 has been expandedto its maximum anatomic extent as the spine has reached ligamentotaxis.The surgeon would then terminate the insert insertion procedurereleasing handle 36, and then removing the inserter 10 from the expandeddevice 100 by rotatably removing knob 22 from the proximal end of guidepin 20. As shown in FIG. 10, the guide pin 20 may remain releasablyconnected to expanded device 100 to serve as a locator for subsequentattachment to an apparatus containing suitable bone growth material toassist in the delivery of such material into a channel 114 c of inferiorendplate 114 through which inserts 200 were inserted.

Having described the inserter 10 and the method of expanding aninterbody fusion device 100 and inserting thereinto one or more inserts200 with reference to device 100 wherein a first insert 200 has beenpositioned between superior endplate 112 and inferior endplate 114, itshould be appreciated that the inserter 10 and method may also be usedto introduce insert 200 initially between superior endplate 112 andinferior endplate 114.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe invention are desired to be protected. For instance, while thelifting platform 24 has been described herein as being movable axiallyrelative to a fixed elevator 26, it should be appreciated that liftingplatform 24 may be held in a fixed axial position while the elevator 26is moved axially relative thereto. Also, while the illustratedembodiments have been directed particularly to interbody fusion of thespine, the expandable devices and inserts disclosed herein may be usedin other applications that require distraction of tissue surfaces, suchas, for example, vertebral compression fracture treatments.Modifications in size may be necessary depending upon the body spacebeing distracted.

1. An inserter for expanding an expandable spinal interbody fusiondevice and inserting an insert therewithin, said device including asuperior endplate having an outer surface configured to contact a firstvertebral body of a spine and an inferior endplate movable relative tosaid superior endplate in an expansion direction, said inferior endplatehaving an outer surface configured to contact a second opposingvertebral body of said spine, comprising: an elongate barrel having adistal end and a proximal end, said distal end being releasablyattachable to said device and comprising a trigger actuator at saidproximal end, said barrel including at said distal end a liftingplatform for engaging said superior endplate and an elevator forengaging said inferior endplate, said lifting platform being movabletranslationally relative to said elevator in a direction transverse tothe direction of expansion of said device to cause during suchtranslational movement said lifting platform to move away from saidelevator in the direction of expansion and thereby lift said liftingplatform relative to said inferior endplate and expand said device, oneof said lifting platform and said elevator being operably coupled tosaid trigger actuator to cause said translational movement uponoperation of said trigger actuator, and said barrel movably supportingat least one insert insertable upon operation of said trigger actuatorinto said device between said superior endplate and said inferiorendplate after expansion of said device, said barrel supporting a drivercoupled to said trigger actuator for translational movement relative toone of said lifting platform and said elevator, said driver having adistal end defining a pushing surface for engagement with a cooperativepushing surface on said insert.
 2. The inserter of claim 1, wherein saidlifting platform and said elevator comprise cooperating ramps that uponrelative translation of said lifting platform and said elevator causesaid ramps to cooperatively engage and move said lifting platform andsaid elevator relatively away from each other in the direction ofexpansion.
 3. The inserter of claim 2, wherein said lifting platform iscoupled to said trigger actuator for translational movement and saidelevator is attached to said barrel in a fixed position.
 4. The inserterof claim 3, wherein said driver is coupled to said trigger actuator fortranslational movement relative to said elevator.
 5. The inserter ofclaim 4, wherein said lifting platform includes an upper surface forsupporting said insert and a lower opposing surface defining saidcooperating ramps.
 6. The inserter of claim 5, wherein said driver andsaid lifting platform are coupled to said trigger actuator to moveindependently upon operation of said trigger actuator.
 7. The inserterof claim 6, wherein said driver and said lifting platform are coupled tosaid trigger actuator to move independently of each other upon operationof a single stroke of said trigger actuator.
 8. The inserter of claim 7,wherein said lifting platform is coupled to said trigger actuator tomove before movement of said driver and cause said superior endplate tolift relative to said inferior endplate.
 9. The inserter of claim 8,wherein said lifting platform is coupled to said trigger actuator tohold the position of said superior endplate in a lifted positionrelative to said inferior endplate during operation of said triggeractuator while said driver is moved during such operation to push saidinsert at least partially between said superior endplate and saidinferior endplate.
 10. The inserter of claim 9, wherein said liftingplatform is coupled to said trigger actuator to retract said liftingplatform towards said elevator after said insert is positioned at leastpartially between said superior endplate and said inferior endplate,said driver being coupled to said trigger actuator to advance saidinsert thereafter substantially fully between said superior endplate andsaid inferior endplate.
 11. The inserter of claim 10, wherein saidlifting movement of said lifting platform relative to said elevator,said translational movement of said driver insert for pushing saidinsert into said device and said retraction movement of said liftingplatform towards said elevator are effected in a single operationalstroke of said trigger actuator.
 12. The inserter of claim 11, whereinsaid trigger actuator comprises a linkage mechanism that substantiallyprevents translational movement of said driver until the liftingmovement of said lifting platform is completed.
 13. The inserter ofclaim 12, wherein said barrel movably supports a further insertinsertable upon operation of said trigger actuator between said at leastfirst insert and said inferior endplate.
 14. An apparatus for use inspinal interbody fusion, comprising: an expandable interbody fusiondevice including an inferior endplate having an outer surface configuredto contact a vertebral body of the spine, a superior endplate having anouter surface configured to contact an opposing vertebral body of saidspine, said inferior endplate and said superior endplate being movablerelative to each other in a direction of expansion, said deviceincluding at least one insert insertable into said device between saidinferior endplate and said superior endplate upon expansion of saiddevice; and an elongate inserter having a distal end and a proximal end,said distal end of said inserter being releasably attached to saiddevice, said inserter including an actuator at said proximal end, saidinserter comprising a lifting platform operably coupled to said actuatorfor engaging and lifting one of said superior endplate and an insertwithin said device, and a driver operably coupled to said actuator toinsert said at least one insert into said device, said inserterincluding an elongate track linearly supporting a plurality of insertsfor sequential insertion into said device one below the other.
 15. Theapparatus of claim 14, wherein said inserter comprises an elevator atsaid distal end, said elevator having an upper surface and a lowersurface, said lower surface being in engagement with an interior surfaceof said inferior endplate.
 16. The apparatus of claim 15, wherein saidlifting platform has a lower surface, the lower surface of said liftingplatform and the upper surface of said elevator comprising cooperativelyengaging ramps.
 17. The apparatus of claim 16, wherein said elevator isdisposed in a fixed position relative to said inferior endplate and saidlifting platform is coupled to said actuator for translational movementrelative to said elevator upon operation of said actuator to cause saidramps to cooperatively engage and thereby move said lifting platform andsaid elevator relatively away from each other in the direction ofexpansion.
 18. The apparatus of claim 14, wherein said actuatorcomprises a trigger actuator including a handle and a bar linkagemechanism pivotally coupled thereto.
 19. The apparatus of claim 14,wherein said apparatus further comprises a guide pin releasablyconnected to said device and detachably connected to said inserter. 20.The apparatus of claim 14, wherein said at least one insert comprises alocking structure to interlock said at least one insert to said superiorendplate upon insertion into said device.
 21. The apparatus of claim 20,wherein said at least one insert comprises a locking structure tointerlock said at least one insert to a subsequent insert inserted belowsaid at least one insert. 22-25. (canceled)
 26. A method of expanding anexpandable spinal interbody fusion implant, in situ, said deviceincluding an inferior endplate having an outer surface configured tocontact a vertebral body of the spine, a superior endplate having anouter surface configured to contact an opposing vertebral body of saidspine, said inferior endplate and said superior endplate being movablerelative to each other in a direction of expansion, comprising the stepsof: releasably attaching a distal end of an inserter to said device,said inserter including an actuator at a proximal end thereof; initiallyoperating said actuator to cause said inferior endplate and saidsuperior endplate to move relative to each other in a direction ofexpansion to expand said device; and inserting a first insert movablysupported by said inserter into said device after expansion of saiddevice between said inferior endplate and said superior endplate; andthen further operating said actuator to cause said superior endplate andsaid first insert to move jointly relative to said inferior endplate tofurther expand said device, and after said further expansionsequentially inserting a second insert movably supported by saidinserter directly between said first insert and said inferior endplate.27. The method of claim 26, wherein said first insert and said secondinserts are supported linearly by said inserter immediately adjacenteach other, and wherein after said device is expanded in the initialoperating step said first insert is inserted directly between saidsuperior endplate and said inferior endplate.
 28. The method of claim27, further including the step of determining whether said expandeddevice is capable of receiving a further insert prior to insertion ofsaid further insert between said inferior endplate and said superiorendplate.
 29. The method of claim 28, wherein said determining step iseffected by tactile feedback through said actuator.
 30. The method ofclaim 29, wherein said actuator comprises a trigger actuator including ahandle and a linkage mechanism, and wherein the expansion of said deviceand the insertion of said at least one insert into said expanded deviceis effected in a single operational stroke of said trigger actuator. 31.A method of expanding an expandable spinal interbody fusion implant, insitu, said device including an inferior endplate having an outer surfaceconfigured to contact a vertebral body of the spine, a superior endplatehaving an outer surface configured to contact an opposing vertebral bodyof said spine, said inferior endplate and said superior endplate beingmovable relative to each other in a direction of expansion, comprisingthe steps of: releasably attaching a distal end of an inserter to saiddevice, said inserter including an actuator at a proximal end thereofand an elongate track therebetween supporting a plurality of inserts,each insert having a thickness in the direction of expansion; operatingsaid actuator for the individual insertion of said plurality of inserts,during said operation causing the inferior endplate and the superiorendplate to move apart relative to each other in the direction ofexpansion independently of the insertion of each insert and creating foreach insert an incremental space in the expanded device of dimension notless than the thickness of an insert; and sequentially individuallyinserting said plurality of inserts into a respectively createdincremental space.
 32. The method of claim 31, wherein a firstincremental space is created directly between said inferior endplate andsaid superior endplate for the insertion of a first insert.
 33. Themethod of claim 32, wherein a second incremental space is createddirectly between said inferior endplate and said first insert for theinsertion of a second insert, said first insert and said superiorendplate having been moved jointly relative to said inferior endplateupon the operation of said actuator.
 34. The method of claim 33, furtherincluding the step of determining whether said expanded device iscapable of receiving a third insert prior to insertion of said thirdinsert between said inferior endplate and said second insert asdetermined by tactile feedback through said actuator.